1. Field of the Invention
The present invention relates to a technology of a low-density parity-check (LDPC) code for a transmission channel, particularly to a cyclic comparison method for an LDPC decoder.
2. Description of the Related Art
The low-density parity-check (LDPC) code is a promising and very useful encoding technology with highly complicated calculation. The Min-Sum algorithm thereof can greatly reduce the hardware complexity of a decoder. However, a little performance loss may occur in the operation thereof. Therefore, it is an important subject how to reduce operational complexity via the Min-Sum algorithm without the penalty of performance.
The operation of an LDPC decoder is an iterative process. Refer to FIG. 1 a flowchart of the decoding process of an LDPC decoder. As shown in FIG. 1, the decoder is initialized firstly in Step S10; next, check nodes and bit nodes are respectively updated in Step S12 and Step S14; then, in Step S16, it is checked whether the iteration number exceeds a predetermined maximum iteration number or whether the decoded information bits satisfies the check matrix constraint: HxT=0; if the result is positive, the decoded bits are output, and the process ends, as shown in Step S18; it the result is negative, the process returns to Step S12 to repeat the updates of the check nodes and the bit nodes. From the foregoing description, it is known that the check node unit (CNU) has a great influence on the decoder. The conventional technologies cannot apply to an arbitrary input number of a CNU but can only get an optimal result for a specified input number. In the conventional technologies, the greater the input number, the more the comparisons. Thus, the comparators need increasing, and the CNU operation speed slows down, which will consume more resource. Besides, the conventional technologies did not propose the detailed method for optimizing comparators, which makes them hard to outstand.
Accordingly, the present invention proposes a cyclic comparison method for an LDPC decoder to solve the abovementioned problems.